The present invention relates, in general, to methods for controlling field emission displays, and, more particularly, to methods and circuits for maintaining constant emission current in field emission displays.
Field emission displays are well known in the art. A field emission display includes an anode plate and a cathode plate that define a thin envelope. The cathode plate includes column electrodes and gate extraction electrodes, which are used to cause electron emission from electron emitter structures, such as Spindt tips.
During the operating life of a field emission display, the emissive surfaces of the electron emitter structures can be altered, such as by chemically reacting with contaminants that are evolved from surfaces within the display envelope. The contaminated emissive surfaces typically have electron emission properties that are inferior to those of the initial, uncontaminated emissive surfaces. In particular, contamination causes the electron emission current to decrease for a given set of operating parameters.
It is known in the art to provide a uniform and constant electron emission current by coupling a current source to each of the electron emitter structures. The current source is controlled to provide the desired emission current. However, this scheme can result in a complicated device that is difficult to fabricate and difficult to control.
Accordingly, there exists a need for a method and means for controlling the emission current in a field emission display, which is simple fabricate, easy to control, and extends the operational lifetime of the display.